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Validation Of Mechanical Sampling Systems - Bias Test
Sampling and statistical evaluations for bias testing of mechanical sampling systems are performed according to the methods specified in ASTM D 7430 (Part D). The bias defined in this practice is based on comparing the differences between the test results obtained from the mechanical sampling system population mean and the values obtained from another sampling method (stopped belt) that considered as a reference.
For each characteristic tested, the measurement differences between the obtained mechanical system value and the reference value are calculated, and using the statistical procedures described in the practice, the differences obtained from each set are investigated for evidence of bias between the mechanical system and reference measurements.
Thus, it is possible to provide an estimate of the bias of the mechanical system used for coal sampling. Bias of the mechanical sampling system in coal quality measurement can lead to significant commercial and environmental consequences. Changes in the operation of the sampling system can affect test results. If the deviation is unacceptable, this procedure can enable a review and improvement of the system and its components. Proving that there is no deviation in the system is important in terms of commercial and environmental consequences.